Corporate and other private networks often provide external access outward and inward through Internet gateways, firewalls or other routing devices. It is important for these routing devices to defend the private network against attackers from the outside as well as to allow access to the private network by authorized users. However there are numerous forms of attack on conventional routing device that can incapacitate the devices and interfere with an associated private network. The problem of keeping unauthorized persons from accessing data is a large problem for corporate and other information service management. Routing devices, such as gateways, firewalls and network routers lack important safeguards to block or prevent attacks. In particular, the number of denial service attacks have risen dramatically in recent years. Further, IP spoofing incidents occur with increasing frequency.
A denial of service attack consists of repeatedly sending requests for connections to different hosts through and/or behind the routing device. Typically, the host will wait for acknowledgment from the requester. Because a host can only handle a finite number of requests (for example, 1 to n, where n depends on the resources available to the host), the attacker can crash or “flood” a host with requests to the point of disrupting network service (host/server/port) to users.
Another form of attack is address spoofing which can be used by unauthorized third parties to gain access to a private network. This attack involves the attacker identifying a valid internal network address within the private network. The attacker then requests access to the private network through the routing device by spoofing that internal network address. Conventional routing devices typically are not sophisticated enough to determine that such a request should be denied (i.e., because an external request can not originate from an internal address) and will allow access to the attacker. Address spoofing attacks can be carried out against various types of networks and network protocols such as IPX/SPX, MAC layer, Netbios, and IP.
It is therefore advantageous to provide facilities within a routing device that block denial of service, address spoofing and other attacks on an associated private network.